Hi,
I'm currently working on a library for use on LPC15xx microcontrollers, part of the library is a CAN module and I'm seeing some really strange behaviour.
To better explain what I have, I have two stages to the library. The CAN module of the higher level library is built on a lower level CAN library I wrote to the Canpie spec, but the higher level library has a lot of other stuff like generic interfaces to GPIO, timers, UART etc.
Now when I test just the low level Canpie library functions, everything works fine. But when I use my higher level library the data segments in my CAN packets are not what they should be. The higher level library calls the exact same functions as my Canpie test does as well. Right now I'm trying to pass a CAN packet full of 0's in the data segment (DLC of 8) but my output has occasional bits changed or simply doesn't give out a valid CAN packet, though the ID is always fine. I really have no idea what could be causing this and would appreciate any help. I'm worried it could be some sort of memory or stack issue, but the DA registers on the C_CAN0 peripheral never go non-zero as far as I can see in debugging so I still have no idea what it could be.
I've attached a sample of the output I get from my Salae logic analyser, hooked up to the TX pin on the LPC1549 dev board, reminder that the data should be all zeroes. In case it helps anyone.
| Time [s] | Analyzer Name | Decoded Protocol Result |
| 2.255614 | CAN | Extended CAN Identifier: 405898241 |
| 2.255686 | CAN | Control Field: 8 bytes |
| 2.255694 | CAN | Data Field Byte: 0 |
| 2.255714 | CAN | Data Field Byte: 0 |
| 2.255732 | CAN | Data Field Byte: 0 |
| 2.255752 | CAN | Data Field Byte: 0 |
| 2.255772 | CAN | Data Field Byte: 8 |
| 2.255788 | CAN | Data Field Byte: 0 |
| 2.255808 | CAN | Data Field Byte: 0 |
| 2.255826 | CAN | Data Field Byte: 0 |
| 2.255846 | CAN | CRC value: 20654 |
| 2.255878 | CAN | NAK | |
| 3.149655 | CAN | Extended CAN Identifier: 405898241 |
| 3.149727 | CAN | Control Field: 8 bytes |
| 3.149735 | CAN | Data Field Byte: 0 |
| 3.149755 | CAN | Data Field Byte: 0 |
| 3.149773 | CAN | Data Field Byte: 0 |
| 3.149793 | CAN | Data Field Byte: 0 |
| 3.149813 | CAN | Data Field Byte: 8 |
| 3.149829 | CAN | Data Field Byte: 0 |
| 3.149849 | CAN | Data Field Byte: 0 |
| 3.149867 | CAN | Data Field Byte: 0 |
| 3.149887 | CAN | CRC value: 20654 |
| 3.149919 | CAN | NAK | |
| 4.220714 | CAN | Extended CAN Identifier: 405898241 |
| 4.220786 | CAN | Control Field: 8 bytes |
| 4.220794 | CAN | Data Field Byte: 0 |
| 4.220814 | CAN | Data Field Byte: 0 |
| 4.220832 | CAN | Data Field Byte: 0 |
| 4.220852 | CAN | Data Field Byte: 0 |
| 4.220872 | CAN | Data Field Byte: 8 |
| 4.220888 | CAN | Data Field Byte: 0 |
| 4.220908 | CAN | Data Field Byte: 0 |
| 4.220926 | CAN | Data Field Byte: 0 |
| 4.220946 | CAN | CRC value: 20654 |
| 4.220978 | CAN | NAK | |
| 5.03876 | CAN | Extended CAN Identifier: 405898241 |
| 5.038832 | CAN | Control Field: 8 bytes |
| 5.03884 | CAN | Data Field Byte: 0 |
| 5.03886 | CAN | Data Field Byte: 0 |
| 5.038878 | CAN | Data Field Byte: 0 |
| 5.038898 | CAN | Data Field Byte: 1 |
| 5.038916 | CAN | Data Field Byte: 0 |
| 5.038934 | CAN | Data Field Byte: 0 |
| 5.038954 | CAN | Data Field Byte: 0 |
| 5.038972 | CAN | Data Field Byte: 0 |
| 5.038992 | CAN | CRC value: 20654 |
| 5.039024 | CAN | NAK | |
| 5.869806 | CAN | Extended CAN Identifier: 405898241 |
| 5.869878 | CAN | Control Field: 8 bytes |
| 5.869886 | CAN | Data Field Byte: 0 |
| 5.869906 | CAN | Data Field Byte: 0 |
| 5.869924 | CAN | Data Field Byte: 0 |
| 5.869944 | CAN | Data Field Byte: 0 |
| 5.869964 | CAN | Data Field Byte: 8 |
| 5.86998 | CAN | Data Field Byte: 0 |
| 5.87 | CAN | Data Field Byte: 0 |
| 5.870018 | CAN | Data Field Byte: 0 |
| 5.870038 | CAN | CRC value: 20654 |
| 5.87007 | CAN | NAK | |
| 6.634848 | CAN | Extended CAN Identifier: 405898241 |
| 6.63492 | CAN | Control Field: 8 bytes |
| 6.634928 | CAN | Data Field Byte: 0 |
| 6.634948 | CAN | Data Field Byte: 0 |
| 6.634966 | CAN | Data Field Byte: 0 |
| 6.634986 | CAN | Data Field Byte: 0 |
| 6.635006 | CAN | Data Field Byte: 8 |
| 6.635022 | CAN | Data Field Byte: 0 |
| 6.635042 | CAN | Data Field Byte: 0 |
| 6.63506 | CAN | Data Field Byte: 0 |
| 6.63508 | CAN | CRC value: 20654 |
| 6.635112 | CAN | NAK | |
